Process for fabricating weatherseals

ABSTRACT

A process for forming linear, thermoplastic weatherseals into a bend position is provided which avoids buckling of the thinner surfaces of the weatherseal material. The process involves the use of a support insert which supports the thinner surfaces during the bending operation, and thus assists in preventing the deformation of the thinner weatherseal surfaces. The support is preferable constructed of a material which is unaffected by temperatures higher than the heat-deformation temperature used to set the weatherseal material into a bent configuration, and thus, the support insert retains its linear shape when removed from the bending press, and therefore, can be reused. An improved process for manufacturing bent thermoplastic weatherseal material results.

FIELD OF THE INVENTION

The present invention relates to the field of weatherseals, and inparticular, relates to a process for the fabrication of weatherseals forautomotive use.

BACKGROUND OF THE INVENTION

Weatherseals, in automotive applications, are primarily used to providea seal against wind, rain, noise and the like, in situations whereinglass and metal (or other materials) are in contact with each other (infixed or movable situations), or in situations where metal components(or other materials) are in a movable relationship to one another, suchas, for example, a door, trunk or hood opening with respect to the frameor body of the automobile.

Over the years, a wide variety of weatherseal materials have beenproposed and used, including rubber, synthetic rubber, rubberizedmaterials, plastics, elastomers and the like. A typical weathersealmight be fabricated of, for example, elastomers, which can be defined asa material which experiences large reversible deformations underrelatively low stress. Some examples of commercially availableelastomers include natural rubber, ethylene/propylene (EPM) copolymers,ethylene/propylene/diene (EPDM) copolymers, styrene/butadienecopolymers, chlorinated polyethylene, and silicone rubber.

Thermoplastic elastomers are elastomers having thermoplastic properties.That is, thermoplastic elastomers are optionally molded or otherwiseshaped and reprocessed at temperatures above their melting or softeningpoint. One example of thermoplastic elastomers isstyrene-butadiene-styrene (SBS) block copolymer. SBS block copolymersexhibit a two phase morphology consisting of glassy polystyrene domainsconnected by rubbery butadiene segments. At temperatures between theglass transition temperatures of the butadiene midblock and the styreneendblocks the SBS copolymers act like a crosslinked elastomer.

In contrast, thermoset elastomers are elastomers having thermosetproperties. That is, thermoset elastomers irreversibly solidify or “set”when heated, generally due to an irreversible crosslinking reaction. Twoexamples of thermoset elastomers are crosslinked ethylene-propylenemonomer rubber (EPM) and crosslinked ethylene-propylene-diene monomerrubber (EPDM). EPM materials are made by copolymerization of ethyleneand propylene, and are typically cured with peroxides to give rise tocrosslinking, and thereby induce thermoset properties. EPDM materialsare linear interpolymers of ethylene, propylene, and a nonconjugateddiene such as 1,4-hexadiene, dicyclopentadiene, or ethylidene norbomene.EPDM materials are typically vulcanized with sulfur to induce thermosetproperties, although they alternatively are optionally cured withperoxides.

Of specific interest in the process of the present invention, however,are weatherseals which comprise materials commonly referred to asthermoplastics and more particularly to “thermoplastic vulcanizates”(TPVs), and even more particularly to weatherseals made from extrudableTPVs.

Thermoplastic vulcanizates (TPV's) are polyolefinic matrices, preferablycrystalline, through which thermoset elastomers are generally uniformlydistributed. Examples of thermoplastic vulcanizates include EPM and EPDMthermoset materials distributed in a crystalline polypropylene matrix.One example of a commercially available material is Santoprene™.thermoplastic rubber which is manufactured by Advanced Elastomer Systemsand is a mixture of crosslinked EPDM particles in a crystallinepolypropylene matrix. These materials have found utility in manyapplications which previously used vulcanized rubber, e.g. hose,gaskets, and the like. In these applications, TPV's are noted for theirability to be processed as thermoplastics while retaining the excellenttensile and compression set properties of vulcanized rubbers.

Commercial TPV materials are typically based on vulcanized rubbers inwhich a phenolic resin or sulfur cure system is used to vulcanize, thatis to crosslink, a diene copolymer rubber by way of dynamicvulcanization, that is crosslinking while mixing (typically vigorously),in a thermoplastic matrix. Sulfur or a phenolic resin is preferred overperoxide free radical cure systems because peroxide degrades apolypropylene or and crosslinks a polyethylene as well as the rubber andthis is in turn limits the extent of rubber crosslinking that can occurbefore the entire mixture degraded or crosslinked and is no longerthermoplastic.

The thermoplastic material of use in the present invention, ispreferably extrutable, and thus forms a thermoplastic extrudate. Thethermoplastic extrudate is preferably a solid material which isessentially free of macroscopic voids, or alternatively, is a dense foammaterial having a density in the range greater than about 80% of that ofthe solid material. It should be noted, however, that the thermoplasticmaterial of interest in the present invention is typicallyre-processable, unlike a thermoset resin.

By “extrudable” is meant that a material blend can be processed in anavailable, commercial extruder or injection moulding machine whichprovides internal mixing at a temperature in the range from, forexample, about 180° C. to 240° C. with a residence time less than 5 min,preferably in the range from 30 sec to 2 min. In thermoplastics such asTPVs, which are typically “self-cured” and not physical blends, theircombination of desirable elastic and thermoplastic properties depends onthe respective amounts of “hard” and “soft” phases provided by eachcomponent, and the properties of each component. The polyolefin phase isthe continuous “hard” phase in which the rubber “soft” phase is presentas discrete particles. By varying the ratios of the components, one mayprovide desired hardness/softness, oil and temperature resistance,oxidation resistance, and extrudability, inter alia.

Through the use of thermoplastic materials, a weatherseal can beproduced which is typically thinner and lighter than weatherseals madeof prior art rubber or rubberized materials. Further, the thinner,lighter, thermoplastic weatherseals can provide reduced wind noise,while still providing good other weatherseal properties such assoftness, abrasion resistance and low coefficients of friction.

The use of TPV materials as weatherseals has been previously describedin, for example, U.S. Pat. Nos. 6,368,700 and 6,277,916. However, whileTPV elastomers are used to produce weatherseals, the ever-increasingdemands of the marketplace necessitate the development of processingthermoplastic weatherseals with improved properties.

In general, the prior art thermoset weatherseal materials would normallybe bent to a desired shape by inserting the linear weatherseal extrudateinto a bending press while heating the material to a temperature aboveits “heat-deformable temperature”. The press can then be used to pressthe material into the appropriate shape. Commonly, this appropriateshape would merely be a right angle bend so that the weathersealmaterial might be placed in, for example, the corner of a window openingin an automotive application.

Because of its thinner, lighter construction, and the differences inchemical thermosetting properties, thermoplastic weatherseals can bemoulded up to 35% faster than prior art EPDM weatherseals. As such, useof thermoplastic weatherseals in bent applications could provideimproved efficiencies.

However, thermoplastic extrudates are commonly used in linear, orstraight-line applications, or in applications, with only minor amountsof bending. Typically, thermoplastic extrudates are not used insituations where bending to over 20° is required since the bendingprocess can adversely affect the weatherseal. It has been observed thatwhen thermoplastic weatherseal materials are bent using the abovedescribed bending process, a common occurrence is for the thinnersections of the extruded weatherseal to “buckle” and otherwise deform.If used in this condition, it would be difficult to achieve aneffective, acceptable seal, and thus, leakage of water and/or anincrease in wind noise would be possible, and would likely be probable.

The buckling effect is most noticeable on thinner sections (in crosssection) of the thermoplastic material being bent, and the amount ofbuckling observed will be dependent on the material utilized, the heatdeformation temperature for that material, the bending temperature use,the amount of time that the material is in the bending press, and thelike. The buckling effect is typically characterized by a wavy, ornon-linear deformation of a previously straight component of theextruded seal, after the bending operation. A typical example of thiseffect would be observed when, for example, an extruded thermoplasticweatherseal was bent 90° to fit in an automotive window or doorapplication. After the bent area had been subjected to the heat andpressure encountered in a bending press, the thinner sections of theweatherseal would have a wavy appearance in the bent area.

To overcome this difficulty, it would be advantageous to provide aprocess for the bending of thermoplastic extrudate weathersealmaterials, in a typical prior art bending device, which would provide abent thermoplastic material with a reduced level of buckling, whencompared to prior art process, and more preferably, would provide aprocess which eliminates the buckling effect essentially completely.

SUMMARY OF THE INVENTION

Accordingly, it is a principal advantage of the present to provide aprocess for bending of thermoplastic weatherseals, and preferably athermoplastic elastomer and in particular, a TPV extrudate weatherseal,which minimizes the buckling effect when the TPV material is bent.

It is a further advantage of the present invention to provide a processfor bending of thermoplastic materials which minimizes the bucklingeffect while using bending devices substantially in accordance with thebending devices of the prior art.

The advantages set out hereinabove, as well as other objects and goalsinherent thereto, are at least partially or fully provided by theprocess of the present invention, as set out herein below.

Accordingly, in one aspect, the present invention provides a process forforming thermoplastic weatherseals into a bent condition comprising:

-   -   a) inserting a bendable support insert into at least a portion        of a linear, straight thermoplastic weatherseal material to        provide a bendable weatherseal assembly;    -   b) inserting the bendable weatherseal assembly into a bending        press, and activating the press in order to bend the weatherseal        assembly into a bent condition;    -   c) heating the weatherseal assembly in the bent condition to a        bending temperature greater than the heat deformation        temperature of the thermoplastic material;    -   d) maintaining the assembly in the press until the thermoplastic        material is set into the bent position; and    -   d) removing the weatherseal assembly from the press, and        removing the support insert from the thermoplastic weatherseal        material. The thermoplastic weatherseal material essentially        maintains the bent condition when removed from the press.

In a further aspect, the present invention also provides a supportinsert for use in the operation of forming thermoplastic weathersealsinto a bent position comprising a base structure manufactured of aflexible material, having at least one face of which corresponds to thesurface of the thermoplastic weatherseal, so as to support theweatherseal during a bending process. The flexible material isessentially non-reactive with the thermoplastic weatherseal.

In a still further aspect, the present invention also provides athermoplastic weatherseal, and preferably a TPV weatherseal, which hasbeen formed to a bent condition using the process of describedhereinabove with respect to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this invention will now be described by way of exampleonly in association with the accompanying drawings in which:

FIG. 1 is a perspective view of an essentially linear thermoplasticextrudate weatherseal;

FIG. 2 is a cross-sectional view of the weatherseal of FIG. 1

FIG. 3 is a perspective view of a bent section of weatherseal which hasbeen bent by a process according to the prior art;

FIG. 4 is a perspective view of a support insert for use in the presentinvention;

FIG. 5 is a perspective view of a weatherseal shown in an open bendingpress;

FIG. 6 is a cross-sectional view of a support insert which is shown inposition in a weatherseal; and

FIG. 7 is a perspective view of a bent section of weatherseal which hasbeen bent by a process according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, there is illustrated a weatherseal referredto generally by reference numeral 10, formed by extruding a selectedthermoplastic elastomer, most preferably TPV available under thetrademark Santoprene. In the present application, the term “weatherseal”refers to a product used for sealing between surfaces, and inparticular, to a thermoplastic material or to a thermoplastic elastomerintended for use in any application where metal and/or glass parts. Thepresent application is primarily directed to the use of thermoplasticand thermoplastic elastomeric materials, and preferably to extruded TPVmaterials (TPV extrudates) in automotive applications. However, theskilled artisan will be aware that weatherseals are used in a widevariety of application. Accordingly, while the present application isdescribed with particular reference to the automotive industry, theskilled artisan would be aware that the present application is equallyapplicable in other non-automotive applications.

With respect to the use of a thermoplastic material for weathersealapplications, the weatherseal may be formed of a thermoplastic material,or may be formed of a blend of materials, comprising thermoplasticmaterial, thermoplastic elastomers and TPV. Other materials for blendingor co-extrusion can include, for example, melt-blended olefin-basedelastomers including polypropylene, polyethylene. Other components caninclude plasticizers, viscosity modifiers such as processing oils oresters, fillers, colourants, curing agents, antioxidants and otheringredients. Suitable fillers can include calcium silicate, clay,kaolin, talc, silica, diatomaceous earth, powdered mica, barium sulfate,aluminum sulfate, calcium sulfate, basic magnesium carbonate, glassfibers, and carbon fibers, provided the filler is used in an amountsmall enough not to adversely affect either the hardness or thecoefficients of friction of the thermoplastic copolymer.

The components of the weatherseal are preferably selected so as toprovide acceptable weatherseal properties with respect to, for example,known weatherseal performance properties such as flexibility,durability, hardness, UV resistance, and the like. The cross-section ofthe body is preferably adapted to be held in or on a particular portionof an opening which is to be sealed against the weather.

Weatherseal 10 generally has a height and width of approximately 2.5 cm,and can be of any desired length. It has a main U-shaped body section 12which is adapted to be snugly fitted around the flange of a metallicframe section (not shown) of an automobile, and in particular, of anautomobile window. The interior of U-shaped body section 12 has lips 16which are used to provide a friction fit and weather resistant seal tothe flange of the window opening of an automobile (not shown). Theweatherseal may also be attached with suitable fastening means (notshown) or with adhesive. The cross-section of the weatherseal will varydepending upon its use, but in general, the U-shaped body section 14provides a linear channel in the extruded thermoplastic weatherseal.

Shown above the main U-shaped body section 12, is a second channel area18 surrounded by weatherseal area 20, which has an opening 22 throughwhich the edge of a glass window would be positioned. At the edges ofopening 22, area 20 includes two relatively thin edge sections 24 and26. Edge sections 24 and 26 provide a seal against the glass insertedinto second channel area 18.

In FIG. 3, a weatherseal 10 is shown in persepective which has been bentin a manner consistent with the prior art, as generally describedhereinbelow with respect to FIG. 5. Of particular note are edges 24 and26. In the bent section 30, the thin edges 24 and 26 have buckled andproduce a wavy appearance. In use, this buckled area would likely notprovide acceptable weatherseal properties.

FIG. 4 provides a perspective view of a support insert 40 of use in thepresent invention. Support insert 40 is made of flexible material,preferably silicon-based material, and is preferably approximately 15 to30 cm in length, depending upon radius and has a profile and height andwidth so as to correspond with, and fit into channel area 18 ofweatherseal 10. Support insert 40 has faces 44 and 46 which act tosupport edges 24 and 26 during the bending process.

In FIG. 5, a bending press 100 is shown which can be used in the processof the present invention. Press 100 comprises a fixed back section 102and a movable centre section 104 which can be moved from an openposition, as shown, wherein linear, extruded thermoplastic weatherseal10 can be inserted into the press 100, to a closed position wherein theweatherseal 10 is bent to the desired angle, as determined by the shapeof the pressing faces of press 100. Shown in position for bending, inaccordance with the process of the present invention, is support insert40. FIG. 6 shows a cross-sectional view of weatherseal 10 with supportinsert 40 in place.

In operation, press 100 is opened and TPV weatherseal 10, with supportinsert 40, is inserted. Press 100 is then closed so that weatherseal 10and support 40 are bent to the appropriate shape.

The support insert 40 is inserted into the thermoplastic weatherseal 10,and acts to form a support against which the surfaces prone to buckling,will rest. During the bending process, the support 40 insert acts tokeep the supported surface in a linear alignment, and facilitates thesetting of the thermoplastic into a non-buckled, bent configuration.

The support insert 40 is made from a flexible material which has a heatdeformable temperature which is above the bending process temperature,and as such, is essentially unaffected by the bend process pressureand/or temperature. Any suitable material can be utilized provided itprovides the support necessary during the pressing operation, andpreferably does not significantly react with, adhere to, or otherwiseaffect the surface of the thermoplastic material being processed.

The support insert 40 should preferably be bendable in order to beinserted into the linear thermoplastic extrudate as a straightcomponent, bent during the bending press, but returning to a straightconfiguration once removed from the bent, thermoplastic extrudate. Assuch, after the pressing operation, the support insert preferablyreturns to its original shape after removal from the thermoplasticmaterial. In this fashion, the support insert 40 is available for reuse.It should be noted that while the support insert 40 might be pre-bent tosome extent, or even to the final bend angle of the press, it ispreferred that the support insert be essentially linear so as tofacilitate insertion of the support insert 40 in a suitable position ina linear extrudate.

The weatherseal 10 is then heated to a temperature above itsheat-deformable temperature, and held at that temperature for asufficient length of time for the weatherseal 10 to permanently take onthe bent shape established in press 100. When the bent shape has beenset, press 100 is opened, weatherseal 10 is removed, and support insert40 is removed. After removal, support insert 40 returns to its originallinear shape, as shown in FIG. 4.

In the process of the present invention, the TPV material is heatedabove its heat-deformable temperature. This temperature is the value atwhich the material becomes essentially permanently set into, in thiscase, a bent position. Without being bound by theory, this temperatureis not a melting temperature, or the like. For ease of processing, atypical heat-deformable temperature for the TPV materials, andpreferably the TPV extrudates, is a temperature of at least 120° C. andpreferably, is in the range of from 120° C. to 150° C. Further, in theprocess of the present invention, the thermoplastic material orextrudate, is placed into a press, similar to presses previously knownwithin this industry. In this press, the weatherseal is heated (if ithas not already been pre-heated) to a temperature above itsheat-deformable temperature. The press is used to exert pressure on thethermoplastic material in order to force the thermoplastic material totake on the desired shape, and in particular for this application, thedesired bend angle.

The pressure exerted on the thermoplastic material is provided merely tobend and hold the thermoplastic into the desired shape while it isheated to (or held at) the heat-deformable temperature. The desired bendis typically an essentially permanent bend of the linear thermoplasticmaterial or extrudate to an angle of between 20° and 180°, and mostpreferably, to an angle of about 90° with about a 2.5 cm to 5.0 cmradius.

FIG. 7 shows a weatherseal which has been bent in accordance with theprocess of the present invention. In contrast to the weatherseal shownin FIG. 3, the weatherseal 10 shown in FIG. 7 is free from buckling onedges 24 and 26 in bend area 30. As such, the weatherseal shown in FIG.7 provides greatly improved performance properties over the bentweatherseal shown in FIG. 3.

The process of the present invention provides a method for bendingthermoplastic weatherseal to complementarily fit a door or window, orthe like, which avoids the buckling problems encountered in the priorart. Thus, the technique herein described allows thermoplasticweatherseals to be used in an increased variety of applications withoutthe need for additional weatherseal corner pieces or special joiningprocessing, and allows the advantages of thermoplastic weatherseals andin particular TPV weatherseals to be used in a greater number ofapplications.

Thus, it is apparent that there has been provided, in accordance withthe present invention, a process for producing bent thermoplasticweatherseals which fully satisfies the goals, objects, and advantagesset forth hereinbefore. Therefore, having described specific embodimentsof the present invention, it will be understood that alternatives,modifications and variations thereof may be suggested to those skilledin the art, and that it is intended that the present specificationembrace all such alternatives, modifications and variations as fallwithin the scope of the appended claims.

1. A process for forming thermoplastic weatherseals into a bentcondition comprising: a) inserting a bendable support insert into atleast a portion of a linear, straight thermoplastic weatherseal materialto provide a bendable weatherseal assembly; b) inserting said bendableweatherseal assembly into a bending press, and activating said press inorder to bend said weatherseal assembly into a bent position; c) heatingsaid weatherseal assembly in said bent position to a bending temperaturegreater than the heat deformation temperature of said thermoplasticmaterial; d) maintaining said assembly in said press until saidthermoplastic material is set into said bent condition; and e) removingsaid weatherseal assembly from said press, and removing said supportinsert from said thermoplastic weatherseal material, wherein, saidthermoplastic weatherseal material essentially maintains said bentcondition when removed from said press.
 2. A process as claimed in claim1 wherein said linear, straight thermoplastic weatherseal material isextruded.
 3. A process as claimed in claim 1 wherein said thermoplasticweatherseal material is TPV.
 4. A process as claimed in claim 1 whereinsaid support insert is manufactured from a silicon based material.
 5. Aprocess as claimed in claim 1 wherein said heat deformation temperatureis greater than 120° C.
 6. A process as claimed in claim 1 wherein saidsupport insert is essentially unaffected by heating to said bendingtemperature.
 7. A process as claimed in claim 1 wherein said weathersealassembly is bent to an angle of between 20° to 180°.
 8. A process asclaimed in claim 1 wherein said weatherseal material has, in crosssection, thin sections which are supported by the surfaces of saidsupport insert.
 9. A support insert for use in the operation of formingthermoplastic weatherseals into a bent position comprising a basestructure manufactured of a flexible material, having at least one faceof which corresponds to the surface of said weatherseal, so as tosupport said weatherseal during a bending process, and wherein saidflexible material is essentially non-reactive with said weatherseal. 10.A support insert as claimed in claim 9, wherein said flexible materialis a silicone based material.
 11. A TPV weatherseal which has beenformed to a bent condition using the process of claim 1.